My invention relates to femoral prostheses and in particular to apparatus for centering a stem of such a prosthesis in the medullary canal of a femur.
Various types of femoral prostheses are known and are used for surgical reconstruction of a femur. In general, these prostheses comprise a ball-shaped head mounted at an anatomical angle on a shank. The shank can be thrust into a medullary canal of a femur to mount the prosthesis on a reserved surface of the femur. Various means of fixation are known, including bone cement, areas of the prosthesis which promote bony ingrowth, and shoulders proximal to the head for preventing the prosthesis from wedging into the medullary canal.
Femoral prostheses are provided in a range of sizes. However, the variation in human anatomy is generally greater than the range of sizes available, or the range of sizes which can be reasonably stocked. To increase the variability of the available of sizes of protheses, sleeves have been proposed which can be placed on the shank of the prosthesis. These sleeves can be of varying thickness and tend to center the shank of the prosthesis in the medullary canal.